According to a known technique, rows of IC chips are mounted on a common substrate and encapsulated in a block of encapsulation material. The entire assembly is then cut to form individual packages. Each individual package contains an IC chip.
Usually, the injection molds include vents made by slots above the face for mounting the IC chips on the substrates. The vents serve for venting the gases formed during injection of the encapsulation material. The width of the slots is determined by the encapsulation material to be injected, and more particularly, according to the dimensions of the filler particles in the encapsulation material. The tendency is to provide slots with narrower and narrower widths. Thus, the venting of gases during the injection of the encapsulation material is becoming more difficult, especially when the mounting face of the substrates is covered with a varnish layer.